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Wetsuits' thermal performance tested

Summary

NPL has performed laboratory and field-based tests for UK wetsuit manufacturer, Spartan, to help further their knowledge of how wetsuits keep people warm.

NPL's specialised measurement equipment (including a guarded hot plate, wireless temperature sensors, and a thermal camera) was used to measure wetsuits' thermal performance. This provides valuable data on how much heat is lost through various parts of the wetsuit, and how quickly that heat is lost.

As anticipated, the lab results confirmed that the main factor in a wetsuit's ability to keep its user warm is the thickness of the material, as opposed to its surface finish. The field tests (which took place on a breezy day in March 2010) on the other hand revealed what happens when wind chill effects become dominant - the surface finish of the wetsuit becomes all-important. The challenge for NPL is to further our understanding of wind chill, by directly measuring its effects.

This information is useful to wetsuit manufacturers because it gives them the much-needed measurement data that can inform their product development, enabling them to make better decisions about the materials and construction methods they use.

This is a great example of NPL's measurement expertise having a positive impact on a UK company's ability to compete in a crowded worldwide market, by solving their measurement challenges.

About the Customer

Spartan is a UK wetsuit manufacturer, who specialise in wetsuits for the wind sports market (i.e. wind-surfing, kite-surfing, and sailing). They are based in Essex and have been making wetsuits since 1958.

The Challenge

There is surprisingly little scientific research into how wetsuits keep people warm. As such, there is very little data that can help manufacturers improve their product design.

Spartan were particularly interested to find out how to improve their windsurfing wetsuits, as these are designed to keep windsurfers warm whilst they are standing up on their board (as opposed to surfers' wetsuits, which are meant to keep them warm whilst underwater).

Spartan and NPL set out to perform some detailed measurements of wetsuits' thermal function, using NPL's sophisticated measurement equipment.

Measuring a wetsuit's thermal function helps manufacturers understand how a wetsuit really works, and therefore allows them to make informed decisions about what materials and construction methods to use.

The Discovery

Spartan's Mark Minter first became aware of NPL through a personal contact. He approached NPL in late 2009 to ask for help in making specialised measurements of wetsuit materials.

The collaborative work was funded under the National Measurement Office's Measurement for Innovators scheme – which helps UK companies solve measurement issues by giving them access to the National Measurement System's facilities (of which NPL is part).

The Journey

In order to provide Spartan with the thermal performance data they needed, NPL decided to perform some initial laboratory-based tests on wetsuit samples, followed by some field-testing of wetsuits during proper use.

The laboratory tests involved measuring the thermal resistance of 4 samples of neoprene cut from a Spartan wetsuit. The four samples were different thicknesses, and their surface finish was either single or doubled lined. NPL's specialised equipment, a piece of kit called a single-sided 305mm guarded hot plate, was used to measure the samples' thermal resistance. This equipment holds the sample of neoprene horizontally inside a chamber, which is then heated from underneath. A detector at the top of the chamber, above the sample, measures how much heat has passed through the sample – this is the sample's thermal resistance value. The results showed that the wetsuits' surface finish had no bearing on how good an insulator it was.

Following the laboratory tests, the team performed some field tests in Clacton, on the Essex coast, far from the controlled laboratory environment of NPL's Teddington site. Instead of using the lab-based guarded hot plate facility, the team used portable wireless sensors and a thermal camera.

Spartan's Mark Minter and John Morgan, and pro-windsurfer Chris Murray donned their wetsuits and joined NPL's Dr Richard Dudley and Dr Rob Simpson on a chilly day in March 2010 to test the wetsuits in their natural habitat – in the sea and on the beach.

Richard and Rob monitored Mark, John and Chris' body temperatures throughout the trial using wireless temperature sensors taped under their right armpits.

The thermal camera was used to measure each man's temperature, in his dry wetsuit, before entering the sea. The three men then spent up to two minutes in the sea, to simulate the short spells of time windsurfers typically spend in the sea, before being measured by the thermal camera again. The men then spent ~10 minutes exercising in the sea, to simulate the longer periods of time surfers and swimmers endure in the water. The fourth and final measurement of the day was taken of the men after they had been standing in their (wet) wetsuits in the cold breeze for ~10 minutes.

What was interesting about the difference between the laboratory and field tests was that, in the lab the wetsuits' surface finish made no difference to how well it insulated against heat loss. But, in the field tests the surface finish had a measurable effect on how well the wetsuit kept its user warm. This difference is caused by wind wicking moisture (and therefore heat) away from the surface of the wetsuit via convection – or 'wind chill'. The effect of wind chill has been recognised for some time, but measuring it in this way increases our understanding of it, and can help wetsuit manufacturers mitigate its effects.

The Impact

The potential impact of this collaborative research is wide-reaching.

In the short term, Spartan will be able to make better wetsuits, more efficiently. Which in turn will hopefully lead to improved customer-satisfaction.

In the longer term, if this work is extended to other wetsuit manufacturers and neoprene suppliers, it could have a huge social impact. Millions of people in the UK spend their leisure time enjoying activities that require wetsuits to brave the often chilly UK waters (such as surfers, scuba-divers, swimmers, tri-athletes, wind-surfers, sailors, kite-surfers etc). Improved wetsuit materials and construction could have a positive impact on these people, allowing them to spend more time in the water, and giving them the freedom to do their sport of choice in much colder conditions than they are currently comfortable doing.

"NPL's wetsuit testing has really helped us gain a better understanding of the technical side of wetsuit design. We are now focused on improving our suits by using the correct materials and fully testing everything before production. Neoprene suppliers send us samples with subjective claims as to a material's suitability for our needs, rather than objective data about its thermal performance. NPL's testing has highlighted the need to research the correct new material and has saved us producing whole ranges of suits (saving us at least £100,000) that would effectively be next to useless for the colder northern European countries we sell to."Mark Minter, Spartan